The present invention relates to optical interconnects for electronic systems wherein the interconnection capability provides for high bandwidth, wavelength division multiplexing and a capability to perform broadcast or multicast transmissions between related circuit board assemblies.
Electronic systems engineers, especially those involved in the development of scalable high bandwidth systems, often provide backplanes and/or midplanes in order to interconnect the circuit assemblies so that information may be switched or shared between the constituent members of the system. Backplanes are an ordinary means of providing such interconnection and midplanes are a special case wherein circuit board assemblies may be connected to both sides of what would otherwise be called a backplane. These terms are used interchangeably herein. However, ordinary electrical backplanes generally do not provide an apparatus suitable for optical transmissions. Further, electrical backplanes generally do not provide a means to multiplex a plurality of optical signals into a single optical signal stream. In addition, a backplane is viewed as a means to communicate information between separate assemblies. The present invention provides a means to connect elements of two different systems as though they shared a common backplane. The present invention also provides a means to facilitate broadcast transmissions among circuit board assemblies within a given system. The present invention also provides a means to facilitate multicast transmissions among circuit board assemblies within a given system wherein a subset of the members of a system may be selected to receive a transmission simultaneously.
In our copending patent application Ser. No. 09/771797 filed Jan. 29, 2001 another optical interconnect apparatus is disclosed. It is envisioned that the invention set forth herein can be used in conjunction with the invention disclosed in the copending application to provide a more complete optical interconnect means.
The present invention comprises a generally planar optical splitter and combiner arrangement with a plurality of optical inputs and a plurality of optical outputs. Optical transmitters are arranged to inject optical signals into the combiner and optical receivers are arranged to detect optical signals emanating from the splitter. The transmitters and receivers can be designed to operate at a plurality of different wavelengths to permit wavelength division multiplexing (WDM), or they can be designed to operate at the same wavelength to permit broadcast transmission or they can be designed to operate as logical subsets of wavelengths to permit multicast transmissions.
In a preferred embodiment, an apparatus according to the invention has a plurality of double-sided plates with multiple optical waveguides converging into a central position on each side of the plates. At the central positions are multiple angled reflectors that serve to combine and split the signals from the multiple waveguides into a single optical signal and from a single optical signal to multiple waveguides.
In accordance with the preferred embodiment, each waveguide on a transmitter side of a given plate carries an optical signal that is spectrally separated from the signals on the other waveguides on the same side of the plate. In this manner, a plurality of spectrally isolated optical signals from a plurality of transmitters can be mixed and directed toward a common receiver plate.
Also in accordance with the invention, each waveguide on the other side of the plate is delivered an equal fraction of the multi-spectral signal incident on its central position.
Further, two or more such double-sided plates are connected together by means of fiber-optic cable or by a periscope-like mechanism to extend the communications facilities from one system to others.
Further, two such plates can be connected together directly to facilitate broadcast transmissions at a single wavelength or at multiple wavelengths within a system.
In alternate embodiments, the splitter and combiner functions are implemented differently but serve to illustrate the scope of the present invention.
It is an object of the invention to provide a means of optically multiplexing and demultiplexing a plurality of spectrally isolated optical signals.
It is an object of the invention to provide wavelength division multiplexing for an easily scalable number of channels from an easily scalable number of circuit board assemblies.
It is an object of the invention to provide wavelength division multiplexing from one system to another system.
It is an object of the invention to provide wavelength division multiplexing within a single system.
It is an object of the invention to provide a broadcast optical medium on which multiple circuit board assemblies can communicate.
Other and further objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in practice.